1. Field of the Invention
The present invention relates to a light transmission touch panel, and more particularly, to a touch panel having capacitance circuits.
2. Description of the Related Art
Touch panels have been widely applied in the fields of household appliances, communications, and electronic information devices. Common applications of the touch panel include an input interface of a personal digital assistant (PDA), an electrical appliance, a game machine, etc. The current trend of integration of touch panel and display panel allows a user to use his or her finger or a stylus to indicate a control icon shown on the panel in order to execute a desired function on a PDA, an electrical appliance, a game machine, etc. The touch panel is also applied in public information inquiry systems to provide an efficient operation system for the public.
A conventional touch panel comprises a transparent substrate having a surface on which sensing zones are distributed for sensing a signal associated with the touch of a user's finger or stylus to effect input and control. The sensing zones are made of transparent conductive membranes, such as Indium Tin Oxide (ITO), and a user may touch the transparent conducive membrane corresponding to a specific location shown on the display to effect operation of the device.
In order to detect the location where a finger or a stylus touches the touch panel, a variety of capacitive touch panel techniques are developed. As shown in FIG. 1A, a touch panel 10 comprises a substrate 11, a first transparent conductive layer 12, an insulation layer 13 and a second transparent conductive layer 14. The first transparent conductive layer 12 is patterned and formed on the transparent substrate 11 by a photolithography process, and includes the plurality of first cells 121 and a plurality of first wires 122 longitudinally connecting first cells 121 that are aligned. The insulation layer 13 is overlaid on the first transparent conductive layer 12 and substrate 11. The patterned second transparent conductive layer 14 is overlaid on the insulation layer 13, and comprises a plurality of second electrode cells 141 and a plurality of second wires 142 transversely connecting the second cells 141 that are aligned. A plurality of connection wires 143 are disposed on a side of the insulation layer 13, whereby each chain of the second cells 141 transversely connected turns toward the bus end of the first leads 122.
FIG. 1B is a cross-sectional diagram along line 1-1 in FIG. 1A. The first transparent conductive layer 12 and second transparent conductive layer 14 are overlapped on the substrate 11, and the insulation layer 13 covers all of the area of the substrate 11. However, each of the first transparent conductive layer 12, the insulation layer 13 and the second transparent conductive layer 14 can absorb some amount of light so that a display with the touch panel 10 appears darker.
FIG. 2 is a cross-sectional diagram of another conventional touch panel. A touch panel 20 comprises a substrate 21, a first transparent conductive layer 22, a first insulation layer 23, a second transparent conductive layer 24, and a second insulation layer 25. The first insulation layer 23 is overlaid on a first transparent conductive layer 22 and the upper surface of the substrate 21, and has the second insulation layer 25 overlaid on a second transparent conductive layer 24 and the lower surface of a substrate 21.
Compared with the touch panel 10 in FIG. 1B, the touch panel 20 needs to be processed on both sides of the substrate 21. Therefore, some issues such as scratch, exposure and ITO etching occur during the specified processes. In addition, the additional second insulation layer 25 can also absorb some light which causes reduced transmittance.
Thus, it is desired to have a touch panel that overcomes the above drawbacks of the conventional touch panels.